Behavioral research has found evidence supporting reward dominance in adolescence with externalizing disorders, but findings from neuroimaging studies have been largely heterogeneous. We examined the Feedback-Related Negativity (FRN) and P3b in relation to self-reported externalizing behavior among 78 adolescents (11-18 yrs) during a monetary gambling task with concurrent high-density electroencephalogram. As expected, the P3b and the FRN demonstrated greater evoked activity to reward and punishment, respectively. Further, high externalizing behavior was associated with greater P3b difference and reduced FRN difference in response to reward and punishment, suggesting that externalizing behaviors may be associated with both reward dominance and reduced feedback-monitoring.